The formation has been hidden under ice for more than four million years.

A previously unknown canyon has been discovered in Greenland, hidden beneath the ice. It is at least 750 kilometers (466 miles) long. To put that in perspective, imagine a ten kilometer (6.2 mile) wide gorge, up to 800 meters (0.5 miles) deep, running from the Southern coast of England and into Scotland. This is on the same scale as parts of the Grand Canyon.

Jonathan Bamber, who led the research, was originally mapping Greenland’s bedrock, which was previously thought to be relatively flat and smooth. “Unexpectedly, we found an enormous apparent formation,” he said. “We looked at it in more detail and realized it was a canyon.”

The canyon, which is thought to predate glaciation, has remained hidden beneath two kilometers (1.2 miles) of ice for more than four million years. It has the characteristics of a meandering river channel, an ancient river system that Bamber thinks hasn’t been significantly modified by ice cover.

It is almost twice the length of the Grand Canyon, half as deep but almost as wide, and certainly the only feature in Greenland this long.

The discovery of such an enormous geographical formation seems astounding today. We’d probably assume that geographical exploration and mapping were exhausted after the development of satellite mapping.

“This really is quite remarkable,” Bamber said. “In an age when you have Google street view covering the entirety of the inhabited world, when virtually every house is mapped—in this context, to discover a geological feature of such scale is astonishing.”

Timothy James, a glaciologist at the University of Swansea, agrees. “This is very exciting news,” he said. “Although, I’m not really surprised.”

“Considerable effort has been put into collecting bed topography of the Greenland ice sheet recently, and there is a lot of data to be processed and interpreted.”

Accuracy is difficult if the bed proves to be highly featured, which now seems to be the case. James explained that there is much more to be discovered. Take the case of the bed data recently released.

“It has a spatial resolution of 1 km [0.6 miles] and vertical error that ranges from ±10 m [32 feet] to ±300 m [984 feet],” he explained. “I’m sure there are many secrets left to discover beneath Greenland’s ice, and likewise in Antarctica.”

3D visualisation, facing South.

Jonathan Bamber, University of Bristol

The data was collected over several decades by NASA and researchers from the UK and Germany. Radio waves of certain frequencies can travel through ice, but they bounce off the bedrock beneath. So researchers sent down pulses of radio energy of this particular frequency. By analyzing this radar data, the team was able to map the topography of the underlying bedrock.

Of course, the area contributes to sea level rise, and therefore the findings should help researchers to understand current changes.

“The canyon is significant when we think about the movement of the underlying water,” said Bamber. “This lubricates the ice sheet and therefore determines the speed at which it moves.”

“We think the canyon is an efficient conduit for ice-melt from the glacier. If you want to model glacial movement—something that is ever more crucial due to global warming—then knowing about such topography is very important.”

The discovery shouldn’t affect our forecasts for future sea level in itself, but it does highlight that we still don’t know everything about the surface of our own planet.

The Conversation
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Regardless. How much of that canyon was "hidden" by ice and how much was "carved" by that ice. It might seem to be splitting hairs but, honestly, it's like saying a dagger is hiding a wound until it begins to withdraw.

EDIT: Lol, I am not reading well this late on a Friday afternoon. Sorry about that! Thought to predate indeed.

So this is really cool and will provide us with some interesting studies (life untouched for 100k years, etc) but I'm even more interested in the global engineering opportunities. Could we dam the canyon such that it would capture most of the ice sheet's meltwater? Since there's no wildlife there should be no objections. If not, could we dam it and pump seawater into it? Just how much?

Regardless. How much of that canyon was "hidden" by ice and how much was "carved" by that ice. It might seem to be splitting hairs but, honestly, it's like saying a dagger is hiding a wound until it begins to withdraw.

Did you miss that bit in the article, or you find it non-credible for some reason?

Josephine Lethbridge wrote:

The canyon, which is thought to predate glaciation, has remained hidden beneath two kilometers (1.2 miles) of ice for more than four million years. It has the characteristics of a meandering river channel, an ancient river system that Bamber thinks hasn’t been significantly modified by ice cover.

That sounds to me like they looked at the shape of the valley and compared it to those known to be created by glaciation and found a poor match.

How much of that canyon was "hidden" by ice and how much was "carved" by that ice. It might seem to be splitting hairs but, honestly, it's like saying a dagger is hiding a wound until it begins to withdraw.

The article states this canyon has the appearance of being carved by a meandering river channel and that it likely predates glaciation. The features left by a sliding glacier are usually different enough from those carved by a stream of water over time that this early assumption is likely correct.

edit: and in fact, the glacial movement that will occur as the ice starts to slide off greenland will likely destroy this topology, so it's great we got a picture of these features before they're erased.

"It is at least 750 kilometers (46.6 miles) long."Just a note: 750 kilometers <> 46.6 miles. Just move the decimal over one place and we are good to go.

Thanks! That really cleared things up. I should have paid more attention to the km, because I was comparing 46 with 277 and shrugging a lot. So now, we need to figure out what makes a canyon grander? Length or width?

this whole "green" movement is getting out of hand. even canyons are going green(land) now. *groan*

agree that it's pretty cool that we get to see (mostly) what it looks like before the glacier scrapes a lot of it away. however, the error bars seem to be pretty huge. +-300m? that's not insignificant!

Next interesting bit to see is how deep it would be once you remove the weight of the ice sheet.Based on the wiki entry for greenland, the ice is thickest almost at the same place this is at it's lowest, meaning this area potentially stands to rebound the most.

Was it me or was the margin for error looking pretty big? Up to +/- 300m out of 800m?

"League" doesn't appear to have a consistent, agreed value, but is usually taken (in English, at least) to be about 3 miles -- 3 miles being a typical 1 hour walk, or the distance to the horizon (3 nautical miles) seen from "typical" eye hight when standing at sea-level)

For Jules Verne's day, in France, apparently a "league" was about 4 kilometres (2 1/2 miles).

The ancient Roman league was precisely 1 1/2 Roman miles (a Roman mile was about 10% shorter than our own).

Cool, now all we have to do is wait 50 years for the icecaps to melt so we can get a really good look at it.

I'm sure this was tongue in cheek but the researchers studying the greenland ice sheets don't predict significant amounts of the ice sheet to melt away for hundreds of years and 3000 years for it all to melt. The ice above the canyon is over a km thick so unless we drill into it we won't see the canyon this millenium.

From topography it is pretty easy to tell the difference between valleys created by liquid water and valleys created by ice. In section, glaciers carve relatively wide, U-shaped valleys (like Yosemite) while rivers make narrower V-shaped valleys. Also glacial valleys follow gentler curves in plan because ice can't turn corners as sharply as liquid water can.

So this is really cool and will provide us with some interesting studies (life untouched for 100k years, etc) but I'm even more interested in the global engineering opportunities. Could we dam the canyon such that it would capture most of the ice sheet's meltwater? Since there's no wildlife there should be no objections. If not, could we dam it and pump seawater into it? Just how much?

To answer my own question, according to the numbers posted in the article, the volume of the canyon is only .2% of the volume of ice and could only hold the next 30 years of predicted meltwater. That said, if the usable volume (with the addition of several hoover like dams) was even half that it could provide tremendous amounts of hydroelectric energy when full (and when release would be necessary anyway to prevent topping).

"It is at least 750 kilometers (46.6 miles) long."Just a note: 750 kilometers <> 46.6 miles. Just move the decimal over one place and we are good to go.

Thanks! That really cleared things up. I should have paid more attention to the km, because I was comparing 46 with 277 and shrugging a lot. So now, we need to figure out what makes a canyon grander? Length or width?

"It is at least 750 kilometers (46.6 miles) long."Just a note: 750 kilometers <> 46.6 miles. Just move the decimal over one place and we are good to go.

Thanks! That really cleared things up. I should have paid more attention to the km, because I was comparing 46 with 277 and shrugging a lot. So now, we need to figure out what makes a canyon grander? Length or width?

The ancient Roman league was precisely 1 1/2 Roman miles (a Roman mile was about 10% shorter than our own).

And here I thought that a league was the distance that a Roman man or army could walk comfortably in one hour. A league is also 960 rods, 5280 yards or 24 furlongs. A furlong is roughly equal to the old Roman 'stade' (from Greek or Roman hippodrome).